I'm testing Qt5 . I have Qt5 installed at /opt/Qt5.0.1 (still with some Qt4 libraries installed at /usr/lib/i386-linux-gnu/ ) .
However, whenever I tried to run my program, I got the following error message:

I have found the reason. I created a new project, and that one gave me a backtrack.
It's loading the libqt4_plugin.so, which is causing the troubles.
Removing this file from the plugins dir solves the crash!

I copied the plugins dir, removed the gui subdir and set the environment var VLC_PLUGIN_PATH=<new dir>